Paper manufacture



Patented May 18, 1931 I 2,080,437

PAPER MANUFACTURE Harold Robert Rafton, Andover, Mass, assignor to, Rafiold Process Corporation, a corporation of Massachusetts No Drawing, Application October 15, 1934, Serial No. 748,423

26 Claims. (Cl. 9H0) This invention relates to the manufacture of referred to Patent No. 1,914,526, there is disclosed P p a process by which acidic material such as alum The principal object of this invention is the is applied to apaper web containing alkaline filler. manufacture of paper with a substantial degree As substitutes for alum I state that I may use,

Of p yalone or in combination, acidic materials, such 5 An important object of this invention is the as mineral or other acids, particularly metallic manufacture of paper filled with alkaline filler. salts such as compounds of aluminum, zinc, tin,

A further object is the manufacture of paper or .the like. The principal object'of said invenfilled with alkaline filler and having a layer of tion is to provide a method whereby material, filler of higher index of refraction than said alkall chemically incompatible with alkaline filler, such 10 line filler concentrated on at least one surface as acidic material, may retain its effect in a paper thereof and formed substantially in situ. containing alkaline filler; and the process is ap- A further object is the manufacture of paper plicable to both sized and substantially unsized filled with alkaline filler, the alkaline filler par- 1 paper. ticles of which adjacent at least one surface there- In my above copending application Serial No. 5 of, are coated with a layer of substantially water 644,909, which is related in certain respects to insoluble material having a higher index of remy above mentioned Patent No. 1,922,325, I apply fraction than said alkaline filler. a sizing affecting agent to a web containing alka- A further object is the manufacture of amultiline filler and potential sizing; and among the ply paper containing alkaline filler having at at sizing affecting agents I mention are alum, stanleast one surface thereof a concentration of filler nous chloride, lead acetate, and the like. The of higher index of refraction than said alkaline principal object of the invention of said applifiller and formed substantially in situ. cation is to produce sized paper filled with alka- A further object is to produce a paper of very line filler and particularly sized paper made from high opacity filled with alkaline filler. a paper web which contains potential sizing. A further object is to produce a paper of very In my above mentioned copending application high whiteness filled with alkaline filler, Serial No. 646,025, I apply a web affecting agent A further object is in certain cases the redu'cto a. fibrous web containing alkaline filler, being tion or substantial elimination of the two-sided particularly concernedtherein either with subeifect in paper filled with alkaline filler. stantially unsized paper, or with a sized or sub- A further object is to provide an inexpensive stantially unsi P p Containing fibrous method for producing very high opacity and/or other material capable of discoloration or decolvery high white paper filled with alkaline filler. oration by alka An important bj of A further object is the complete exhaustion in t at nv t i to Produce P p at least one the paper web of a reagent otherwise exerting a u ace of which ha a fie nt P v l e, o deleterious or destructive effect thereon. alkaline filler itself or to prevent discoloration Other objects and advantages will become apor decoloration in certain instances in alkaline parent during the course of the following descripfi ed p p A5 Web a fecting agent I Prefer t0 tion. use alum but among others which may be used I This application is a continuation in part of mentionstannous chloride, lead acetate and the my following copending applications: Serial No. ke.

fi d ay 1933; Serial No. 644,909, The three above described copending applicafiled November 29, 1932; and Serial No. 646,025, tions, while they broadly cover'the application of filed December 6,1932; said applications, having web affecting agent or sizing affecting agent, such now matured respectively into Patents Nos. as acidic material, metallic salts and the like to 1,976,743, 1,976,744, and 1,976,745, all issued Oca fibrous web containing alkaline filler, make no tober 16,1934. The present application alsocondisclosure relative to any specific advantageous -tai'ns subject matter related in certain respects effects obtained by employing such materials as to my copending' application Serial No. 675,868, zinc, lead tin, or the like salts over that obtained filed June 14, 1933, and cross reference is made by employing aluminum salts, and it is stated thereto. Cross reference is also hereby made to that in many instances a salt of aluminum such 'my prior Patents 1,914,526, issued June 20, 1933; as alum is the preferred agent.

and 1,922,325, issued August 15, 1933. It is an objectof the present application to dis- In my above referred to copending application close certain specific effects resulting from the Serial No. 672,901, which is a division of my above application of substantially soluble compounds of metals such as zinc, lead, tin, or the like, to a paper web and particularly to a paper'web containing alkaline filler and to claim the novel process and the novel products obtained thereby. Certain similar results obtained by analogous but somewhat modified means will also be disclosed and claimed.

In my above referred to copending-application Serial No. 675,868, I disclose a method of obtaining paper filled with alkaline filler, said paper possessing a high degree of opacity and/or high whiteness, by the application to a fibrous web containing alkaline filler of a preferably thin layer of pigment of a high index of refraction such as zinc, lead, titanium, or the like. Although very satisfactory results can be obtained by the above mentioned method, in certain cases I find that disadvantages may inhere therein in respect to the fact that sometimes the layer of high opacity pigment applied to the web, although fairly well incorporated for most purposes, does not combine with the web to as great a degree as might be desired for certain exacting uses; moreover in certain cases where an adhesive is used in conjunction with the pigment, this gives a surface which differs from the original surface of the paper web, which in certain cases may be undesirable.

While the above method is thus satisfactory in most cases I have found, however, that by the method disclosed herein I can in many instances obtain papers of even better quality than by said method, which papers do not possess certain of the defects which may inhere in papers of the former method, such for example as those above described; and that in certain cases efiects not obtainable by my other method are obtainable by this method. Moreover in certain cases I have found that the present method is more economical of operation and inasmuch as this is a very important factor in papers filled with alkaline filler, which areordinarily of low cost, my invention will result in an increased production of such papers. I

Briefly my invention consists, in its preferred adaptation, of forming or generating a pigment of high opacity in situ, i. e., in the paper web,

rather than adding-such already formed pigment fied metallic salt is applied to a fibrous web containing alkaline filler, it will react with the alkaline filler, resulting in a substantially insoluble compound of the metal in question being formed. For example, if zinc chloride be employed and calcium carbonate is the alkaline filler in the web, an interaction between the two will result in the formation of zinc carbonate, basic zinc carbonate, zinc oxide, hydroxide, or the like on the surface of the calcium carbonate particles and soluble calcium chloride will be concomitantly produced.

It will be apparent that in the above instance the calcium chloride concomitantly produced will remain in part or in whole in the paper web,

and as calcium chloride is a hygroscopic salt,

in many instances this may result in the absorption of water by the paper web after drying; or the giving up of the water with considerable difficulty in the drying process. In some instances this may be advantageous as it would have the tendency to make the paper less quickly subject to change with change in humidity of the surroundings; and in certain instances where a fiexible paper was required, this property might also be of advantage.

However in most cases, especially where the paper is to be used in book and magazine printing which is the use in which the large tonnage of papers filled with alkaline filler is employed, such hygroscopic substances in the web would tend to cause a certain limpness or lack of stiffness, which would be detrimental, as in most cases for such uses a paper with a reasonable degree of stiffness and firmness is desired. Thus, although the concomitant production of a substantially water soluble salt from the alkaline filler of the paper web might in certain instances be desirable, in general I prefer to employ to react with the alkalne filler substantially soluble metallic compounds of such a nature that a substantially water insoluble or at least only very slightly water soluble compound of the metal or metals of the alkaline filler will be formed thereby. For example, if instead of zinc chloride I employ zinc sulphate or preferably zinc sulphate slightly acidified with sulphuric acid as my agent to apply to the paper web, and calcium carbonate as the alkaline filler of the paper web, I produce zinc carbonate, basic carbonate, oxide, hydroxide or the like in conjunction with calcium sulphate, instead of in conjunction with the calcium chloride as in the first instance above 'mentioned. While calcium sulphate is soluble in water to a certain extent, the amount dissolved naturally will depend upon the amount of water present, and inasmuch as the amount of water in a paper web is relatively small and furthermore inasmuch as there is little if any circulation of water in the web so that the calcium sulphate will only come in contact with that water immediately surrounding it, it may under these specific circumstances be considered to be a substantially water insoluble compound.

When a salt of a metal is employed as the agent to be applied to the web, it may thus be seen that I prefer to use a salt, the acid radicle of which is such that it will form a water insoluble or substantially water insoluble compound with-the metallic radical or at least one of the metallic radicals of the alkaline filler in question.

It will be apparent that the reaction of the agent applied to the web will necessarily take place first onthe alkaline filler particles adjacent the surface or surfaces of the web to which the agent is applied, and that the compound or compounds of the interaction will form a coating on the alkaline filler particles, although of course if sufiicient of the agent is present and suflicient time elapses certain individual alkaline filler particles may be completely converted into the reaction product or products which may be formed in the individual case. While, thus, in certain instances some alkaline filler particles at or near the surface may be completely converted, in general the amount of the agent added and the time elapsing before drying will be such that a considerable proportion at least of the particles will be converted into such reaction product or products only on the surface, and the usual result will be that the particles nearer the surface will have heavier coatings thereon than those near the center of the sheet which indeed in many instances may not be reacted upon substantially at all. This local action is of great advantage 7 as it produces a thin deposit of the metallic compound in question at .or adjacent the surface of the paper web, at which point its opacifying efl'ect is possibly at its maximum value, and possibly also its whiteness and/or brightness producing characteristic, which probably would not be the case if, the'effect were concentrated at or equally distributed into the center of the web. As will be seen, there is also a great advantage of having the metallic compound in question deposited chiefly on material already of itself of considerable opacity and whiteness, that is on the alkaline filler, and thus relatively greater effects as to opacity and whiteness are obtained than if the compound itself were applied merely in insoluble form as a pigment to the already formed web such as.is the case in the process disclosed in my above mentioned copending application Serial No. 675,868.

The substantially insoluble compounds of the metals, the substantially soluble compounds of which I employ, have a higher index of refraction than the alkaline filler which is or maybe employed.v I may thus use barium compounds, but inasmuch as barium is a strong basic radicle, and its soluble salts are for the most part neutral or even alkaline, such as the chloride, nitrate, and acetate for example, and thus would best be used in acidified condition, I prefer to use in most cases the metals which are of such a nature that many of the substantially soluble compounds thereof are acidic in nature or maybe brought into solution by the addition of an acid such as the acid corresponding to the acidic radicle of the compound for example, usually in relatively moderate amounts. Such salts are the salts of zinc, which has been mentioned above, the salts of lead, bismuth, antimony, tin, titanium and in certain instances zirconium or some other of the less common and more expensive metals.

As the acid radical of the substantially soluble metallic compound I use, I may employ the chloride, nitrate, acetate, or the like, but I prefer to use those acid radicals which form an insoluble compound or compounds with the metallic radical or at least one of the metallic radicles of the alkaline filler employed, such as sulphate, phosphate, borate, fluoride or the like. These as will be understood form insoluble or substantially insoluble compounds of calcium, if for example calcium carbonate be the alkaline filler employed. As will be apparent, not all the acid radicals above form soluble compounds with all the metallic radicals indicated, or even compounds which are water or acid soluble, so that the acid radical of the compound to be used must be chosen with reference to" the individual metal chosen, which may be readily done by consulting any standard book of reference relative to the solubility of the compounds in question.

Inasmuch as the compounds of titanium have a very high index of refraction, I prefer in many- Another very satisfactory compound I may use is zinc sulphate above referred to, or zinc phosphate preferably in phosphoric acid solution.

Inasmuch as in most instances the papers which I desire to produce are white or substantially white, naturally it is necessary to choose a compound which will produce white or substantially white reaction products withthe alkaline filler employed. Here again, the choice can be easily ascertained by consultation of the standard reference books relative to colors of the compounds produced. E. g. titanium sulphate and zinc sulphate produce white compounds with'an alkaline filler such as calcium carbonate.

Where certain metals form colored or dark colored or even black compounds with materials which may be present in the paper web even though they may not be formed from the alkaline filler itself, naturally in such instances the raw materials entering into the composition of the paper web must be chosen discriminately, or a compound which does not form such colored or black compounds should preferably be employed. For example if lead is being used, care should be taken that no sulphur particles or sulphides are found in the sheet. Otherwise black lead sulphide will be formed. Similarly the dark colcred or black bismuth sulphide would be formed under similar conditions were bismuth salt applied. Such considerations will of course be taken into account by one skilled in the art in applying my invention.

Whereas I have spoken of metallic compounds as the agents to be employed, in certain instances the metals in question exist not as salts but rather as acids or in the acidic radicle rather than in the basic radicle of a compound. Moreover many of the metals which are useful in practicing my invention may act either as a basic or acid radicle according as to whether the compound is acid or alkaline. Thus by applying a compound in which the metal in question is in the acid radicle and which compound is acidic directly to the paper web, there is formed a salt of' the acid in question, for example the calcium salt, without any other concomitant salt of calcium bein produced. Instances of such materials which may be applied are titanic acid and stannic acid. Also the salts of such acids may be used, such as the alkali metal titanates, preferably acidified.

In certain instances the metallic compounds employed are only held in solution by the use of an acid, which sometimes may be of considerable concentration, and in such instances the mere l dilution of the metallic compound with water may bring about a precipitation of most if not all of the metallic compound. For example bismuth chloride is soluble in hydrochloric acid but on dilution bismuth oxychloride is precipitated. Thus for example if a solution of bismuth chloride were applied to a web containing alkaline filler, the bismuth oxychloride would precipitate out to a certain extent at least in the web by dilution with the water of the web apart from any reaction which might take place with the alkaline filler of the web. In certain instances this is very desirable as an extremely fine homogeneous layer of the pigment in question is thus deposited in situ at or near the surface of the paper in addition of course to any material which may be formed as a coating on the alkaline filler particles. In applying such agents, care must be taken not to dilute the material before application because in such case a pre-formed pigment will thus be applied to the surface rather than be precipitated in situ. Pre-formed pigment will thus be applied to the surface as described in my application Serial No. 675,868 rather than be formed in situ as desired according to the present invention. However it is sometimes impossible to avoid a certain or even a considerable precipitating out of a substantially insoluble material from the agent being employed and in such case of course the applying of such pigment as is already precipitated comes within the scope of my c'opending application just above mentioned, whereas the precipitation of the pigment in the web falls within the scope of the present invention.

I have discussed above the precipitation of materals in the web by the reaction of the agent with the alkaline filler in the Web, and have also discussed last above, the precipitation of the agent by materials present in the web independent of the alkaline filler, in the instance mentioned. water being the agent which brings about the precipitation. Other agents in addition to or independent of the water may be employed to bring about such precipitation, for example, soluble salts may be incorporated in the web either in the mix or preferably by application to the paper web either previous or subsequent to the application of the agent in question, whereby precipitation of the agent in question is effected in the web. In certain instances this produces a very satisfactory result and by such means a very satisfactory pigment layer usually at or near the surface is satisfactorily produced. Such a layer may be produced for example by applying alternately to the web a soluble sulphate and a barium salt whereby barium sulphate is produced. Inasmuch as most papers because of the use of alum in their manufacture contain already a certain amount of soluble sulphate, at times this is sufficient to precipitate a certain amount of barium sulphate in the paper, but in most cases it is desirable to add either a larger quantity of soluble sulphate than usual in the fibrous mix or add such sulphate independently to the web preferably as a solution. As will be understood the modification described above of the independent precipitation of the agent in the web may also be carried out jointly with the action of the agent upon the alkaline filler itself in the web.

I prefer, however, the case where the alkaline filler in the web is the entire, or at least part of, the reagent which reacts with the agent applied. One reason for this is that the alkaline filler is always present in the web in excess, and usually in large excess over the agent employed. Thus the agent is exhausted in the web provided suitable concentration be used and sufllcient time be allowed. This is thus an automatic safeguard used are in many cases acidic, and thus possess a deleterious and in many cases a destructive action on the cellulosic content of the paper dur-. ing the drying, and after the paper has dried, it is of great importance thus to assure the exhaustion of the agent, and this uniquely differentiates any process of applying such agent to a paper web containing alkaline filler from the precipitation of an agent by a second reagent in a web not containing alkaline filler, wherein no such automatic exhaustion of the deleterious reagent is provided. Another reason is that referred to above, namely, that by the deposition of the compound as a coating on the alkaline filler particles, an enhanced effect is obtained owing in part to the increased surface obtained of the compound in question.

As indicated above, there are certain of the metals which not only form soluble compounds in acid media or possibly in neutral media but also form soluble compounds in alkaline media. Such compounds are compounds of zinc, tin, lead and the like; for example zincates, plumbates, stannates may be formed, for example of sodium. As will be apparent such compounds may also be employed, in which case however it is necessary to have some acidic constituent present or added to the web in order to effect the precipitation of the compound in question into an insoluble form. Alum is a suitable agent to use in such case.

I have described above certain soluble compounds which hydrolyze to insoluble compounds by the addition of water such as certain salts of bismuth. Likewise certain soluble compounds are changed into insoluble compounds merely by the action of heat, for example certain acetates are thus decomposed, and in many cases heat accelerates an hydrolysis by water which would otherwise take placemore slowly at room temperature. Moreover certain compounds held in solution by ammonia, or as an ammonium compound, are decomposed by heat to an insoluble compound. These changes described may take place either independently in the web or in conjunction with a concomitant action of the agent on the alkaline filler, and they all fall within the scope of my invention. Likewise in certain cases the compounds of the metals in ques tion particularly organic compounds such as those with fatty acids, as soaps, are soluble in organic solvents, and a solution of such may be used to saturate the preferably dry web, with subsequent removal of the solvent. Such treatment, however, while within the scope of my invention, requires special solvent handling and recovery apparatus and distributes the compound throughout the sheet rather than localizes it at or near the surface, and thus I prefer the other methods stated herein for general use.

In certain instances, such as where hydrolysis occurs, but the practice is not confined to this, I may use material, for example colloidalmaterial such as starch, casein, glue, gums, agar agar, and the like, for inhibiting or preventing premature precipitation of an agent, or slowing down such precipitation. This material may be applied directly with the agent to the web, or independently thereof. similar material acting as adhesive may be ap plied to the web with the agent or independent thereof, as in certain instances, especially if a considerable proportion of agent be employed, it may be desirable to employ an adhesive, for example, to avoid or reduce any possible dusting action, and/or to stiffen the web.

I have described in full in my alreadyissued Patents 1,914,526 and 1,922,325 means and methods for applying agents to a paper web and I give further disclosure relative thereto in my copending applications above mentioned. These methods are applicable at present and as cross references have been made to all of these patents and applications, it will be unnecessary to go into the matter in great detail at this point other than to say that the solution may be applied by such -.means as applicator rolls, troughs, sprays, travelling felts, or the like according to the individual case, but in general I prefer an applicator roll Likewise the same or dipping in a trough of material and applying it directly to the paper web, or a spray. As will be apparent the application may take place to one or both sides of the web and it may take place either on the paper machine or as a separate process. Inasmuch as it is more economical to treat the paper in one process I prefer to apply it to the paper web while it is still wet on the paper machine, my preferred point of application being either at the press rolls or at the smooth rolls if the paper machine be so equipped or if not at some point before the paper is completely dried. I may if desired apply the material to the web while it exists at any point on the web-forming device, for example in the web at its early stage of formation in which case there will be more or less comingling of the agent into the web itself according to the stage in which it is applied, or to the web after it has been substantially positioned on the web-forming device either to the under or the top side. Although in certain cases, particularly in the prevention of two-sidedness such application may be very desirable, in general the application to the web after it has left the web-forming device would be the more usual procedure.

As will be apparent my invention may be used in connection with the manufacture of either sized or unsized paper. While I do not limit myself to the alkaline filler content of the papers to be used, this will usually run from about up to 30% or more, and in general, an alkaline filler content of 20-30% is the range most customarily employed.

As will also be apparent, certain phases of my invention, e. g., that in which no action of alkaline filler is necessary for the precipitation of the agent, are equally applicable to paper not containing alkaline filler. Such phases are particularly the application of the agent and its subsequent precipitation by hydrolysis, heat, or the like in the paper web, particularly without the use of a second reactant other than water, or its application in an organic solvent.

In certain other cases, also, as in paper not filled with alkaline filler, such paper web may be treated with a suspension of alkaline filler and then with the agent in question, or in the reverse order, to provide a paper containing the precipitate resulting from reaction of the reagent and alkaline filler, but without any substantial amount of residual alkaline filler being left in the web.

As to,the concentration and amount of the agent to be used, these will naturally depend on the individual agent employed, its solubility, the amounts to be used, the paper machine speed and the like, and will necessarily have to be determined by trial in any given case. However a three to ten percent solution will in most cases be found to be satisfactory, although lesser or greater concentrations may be used. Also an amount of agent which will give from one to five percent by weight of substantially water insoluble pigment in the paper will in general be found to be satisfactory, but here again there will be instances where greater or lesser amounts will be desired.

Where I speak of a compound of high refractiveindex I mean in general a compound having a refractive index higher than that of calcium' carbonate, which is a common alkaline filler, and specifically a compound which has a substantially higher refractive index, such as a compound of barium, and particularly of zinc, lead, tin, antimony, bismuth, titanium, or zirconium, all of which form a number of white or substanally white compounds, and thus white or substantially white paper, to the manufacture of which my invention is particularly directed.

As stated my invention is sometimes useful in diminishing or eliminating two-sidedness in which case the agent may be applied to either or both sides of the web as desired.

By the term alkaline filler I mean substantially water insoluble filler which when agitated in contact with freshly boiled distilled water, .say for an hour, will impart a pH value to such water greater than 7.0, that is, which will be on the alkaline side of the neutral point. Among fillers included in this group may be mentioned calcium carbonate, of which lime mud from the causticizing process is one form; calcium carbonate magnesium basic carbonate employed in the paper disclosed in my U. S. Patent No. 1,595,416 of August 10, 1926; calcium carbonate magnesium hydroxide disclosed in my U. S. Patent No. 1,415,391 of May 9, 1922; and other substantially water insoluble normal or basic carbonates of alkaline earth metals, (which expression is herein intended to include magnesium), or compounds, double salts; or physically associated mixtures of these with one or more other acid soluble materials of a substantially water insoluble nature.

While I use the word paper herein in its broad sense, I am more particularly concerned with the manufacture of printing paper, such as magazine or book paper, to which my invention is particularly adapted. Inasmuch as my invention relates to white or substantially white paper I exclude from the scope of the word paper as used in the claims any paper containing any such quantity of material such as pitch, asphalt or other substitute thermoplastic material as would produce a paper other than that which is known in the trade as white or substantially white paper.

In the claims, where I use the expression deposited in situ, I mean that the material has been so deposited from the agent without the aid of a second reagent, other than possibly water; and where I use the expression generated in situ I mean that the material has been formed in situ by the interaction of a chemical reagent other than water, for example the alkaline filler of the paper web or other reagent, with the agent employed: and similarly where I use the word "depositing" I mean that this is accomplished without the aid of a second agent, other than possibly water; and where I use the word generating I mean that this is accomplished by the interaction of a chemical reagent other than water, for example the alkaline filler of the paper web or other reagent, with the agent employed.

While I have described in detail the preferred embodiments of my invention, it is to be under stood that the details of procedure, the proportions of ingredients, and the arrangement of steps may be widely varied without departing from the spirit of my invention or the scope of the sub-. joined claims.

1. Substantially white paper comprising fibrous material, substantially white substantially water insoluble compound deposited in situ in said paper out of a solution of a compound of a metal selected from the group consisting of barium,zinc, lead, tin, antimony, bismuth, titanium and zirconium, and compound of alkaline earth metal radicle-of an alkaline filler, said last mentioned compound resulting from an action of said solution on said alkaline filler.

2. Substantially white paper comprising fibrous material, substantially white substantially water insoluble compound of titanium deposited in situ in said paper out of a solution of a compound of titanium, and compound of alkaline earth metal radicle of an alkaline filler, said last mentioned compound resulting from an action of said solution on said alkaline filler.

3. Substantially white paper comprising fibrous material, substantially white substantially water insoluble compound of zinc deposited in situ in said paper out of a solution of a compound of zinc, and compound of alkaline earth metal radicle of an alkaline filler, said last mentioned compound resulting from an action on said alkaline filler.

4. Substantially white paper comprising fibrous material and substantially white substantially water insoluble compound of titanium generated in situ in said paper from a solution of a compound of titanium, and from alkaline filler comprising substantially water insoluble alkaline earth metal compound, said alkaline filler being insufiicient in amount to leave any substantial residual amount thereof in said paper.

5. Substantially white paper comprising fibrous material and substantially white substantially water insoluble compound of zinc generated in situ in said paper from a solution of a com pound of zinc, and from alkaline filler comprising substantially water insoluble alkaline earth metal compound, said alkaline filler being insufficient in amount to leave any substantial residual amount thereof in said paper.

6. Substantially white paper filled with alkaline filler which comprises fibrous material, alkaline filler comprising substantially water insoluble alkaline earth metal compound, substantially white substantially water insoluble compound deposited in situ in said paper out of a solution of a compound of a metal selected from the group consisting of barium, zinc, lead, tin, antimony, bismuth, titanium and zirconium, and

' compound of alkaline earth metal radicle of said alkaline filler resulting from an action of said solution on said alkaline filler.

'7. Substantially white paper filled with alkaline filler comprising fibrous material, alkaline filler comprising substantially water insoluble alkaline earth metal compound, and substantially white substantially water insoluble compound generated in situ in said paper from a solution of a compound of a metal selected from the group consisting of barium, zinc, lead, tin, antimony, bismuth, titanium and zirconium, in reaction involving said alkaline filler as a reagent.

8. Substantially white paper filled with alkaline filler which comprises fibrous material, alkaline filler comprising substantially water insoluble alkaline earth metal compound, and substantially white substantially water insoluble compound, said last mentioned compound concentrated adjacent at least one surface of said paper and generated in situ in said paper from a solution of a compound of a metal selected from the group consisting of barium, zinc, lead, tin, antimon-y, bismuth, titanium and zirconium, in reaction involving said alkaline filler' as a reagent.

9. Substantially white paper filled with alkaline filler which comprises fibrous material, alkaline filler comprising substantially water insoluble alkaline earth metal compound, substantially white substantially water insoluble compound,-

said last mentioned compound concentrated adjacent at least one surface of said paper and deposited in situ in said paper from.a solution of a compound of a metal selected from the group consisting of barium, zinc, lead, tin, antimony, bismuth, titanium and zirconium, and compound of alkaline earth metal radicle of said alkaline filler resulting from an action of said solution on said alkaline filler.

10. Substantially white paper filled with alkaline filler which comprises fibrous material, alkaline filler comprising substantially water insoluble alkaline earth metal compound, and substantially white substantially water insoluble compound of titanium generated in situ in said paper from a solution of a compound of titanium in reaction involving said alkaline filler as a reagent.

11. Substantially white paper filled with alkaline filler which comprises 'fibrous material, alkaline filler comprising substantially water insoluble alkaline earth metal compound, and substantially white substantially water insoluble compound of zinc generated in situ in said paper from asolution of a compound of zinc in reaction involving said alkaline filler as a reagent,

12. Substantially white paper filled with alkaline filler which comprises fibrous material, alkaline filler comprising substantially water insoluble alkaline earth metal compound, and. substantially white substantially water insoluble compound of antimony generated in situ in said paper from a solution of a compound of antimony in reaction involving said alkaline filler as a reagent.

13. Substantially white paper filled with alkaline filler, which comprises fibrous material, and alkaline filler comprising substantially water insoluble alkaline earth metal compound, particles of which adjacent at least one surface of said paper have a coating thereon comprising substantially white substantially water insoluble compound generated in situ in said paper from a solution of a compound ofa metal selected from the group consisting of barium, zinc, lead, tin, antimony, bismuth, titanium and zirconium, in reaction involving said particles of alkaline filler as a reagent.

14. Substantially white paper filled with alkaline filler, which comprises fibrous material, .alkaline filler comprising substantially water insoluble alkaline earth metal compound, substantially white substantially water insoluble compound of titanium deposited in situ in said paper out of a solution of a compound of titanium, and compound of alkaline earth metal radicle of said alkaline filler resulting from an action of said solution on said alkaline filler.

15. Substantially white paper filled with alkaline filler, which comprises fibrous material, alkaline filler comprising substantially water insoluble alkaline earth metal compound, substantially white substantially water insoluble compound of zinc deposited in situ in said paper out of a solution of a compound of zinc, and compound of alkaline earth metal radicle of said alkaline filler resulting from an action of said solution on said alkaline filler.

16. Substantially white paper filled with alkaline filler, which comprises fibrous material, alkaline filler comprising substantially water insoluble alkaline earth metal compound, substantially white substantially water insoluble compound of antimony deposited in situ in said paper out of a solution of a compound of antimony, and compound of alkaline earth metal filler comprising substantially water insoluble alkaline earth metal compound, that step which comprises depositing in a paper web substantially white substantially water insoluble compound out of a solution of a compound of a metal selected from the group consisting of barium, zinc, lead, tin, antimony, bismuth, titanium and zirconium, and forming in said web by an action of said solution on an amount of alkaline filler insufficient to leave any substantial residual amount thereof in said web, compound of alkaline earth metal radicle of said alkaline filler.

18. In a method of manufacturing substantially white paper filled with alkaline filler comprising substantially water insoluble alkaline earth metal compound, that step which comprises depositing in a paper web containing such alkaline filler substantially white substantially water insoluble compound out of a solution of a compound of a metal selected from the group consisting of barium, zinc, lead, tin, antimony, bismuth, titanium and zirconium, and forming in said web, by an action of said solution on said alkaline filler, compound of alkaline earth metal radicle of said alkaline filler.

19. In a method of manufacturing substantial- 1y white paper filled with alkaline filler comprising substantially water insoluble alkaline earth of a paper web containing such alkaline filler substantially white substantially water insoluble compound, said last mentioned compound being selected from the group consisting of barium, zinc, lead, tin, antimony,'bismuth, titanium and zirconium compounds, said selected compound being generated from an acid reacting solution of a compound of the metal of said selected compound by reaction with said alkaline filler.

21. In a method of manufacturing substantially white paper filled with alkaline filler comprising substantially water insoluble alkaline earth metal compound, that step which comprises depositing in situ adjacent at least one surface of a paper web containing such alkaline filler substantially white substantially water insoluble compound, out of a solution of a compound selected from the group consisting of barium, zinc, lead, tin, antimony, bismuth, titanium and zirconium compounds, and forming in said web,-

by an action of said solution on said alkaline filler, compound of alkaline earth metal radicle of said alkaline filler.

22. In a method of manufacturing substantially white paper filled with alkaline filler comprising substantially water insoluble alkaline earth metal compound, that step which comprises applying to a paper web containing such alkaline filler a solution of a compound of a metal selected from the group consisting of barium, zinc, lead, tin, antimony, bismuth, titanium and zirconium, salclsolution of said compound being capable of reacting with said alkaline filler to form substantially white substantially water insoluble compound, to form substantially white substantially water insoluble compound by reaction with said alkalinefiller.

23, In a method of manufacturing substantially white paper filled with alkaline filler comprising substantially water insoluble alkaline earth metal compound, that step which comprises applying to a paper web containing such alkaline fillera solution of a compound of a metal selected from the group consisting of barium, zinc, lead, tin, antimony, bismuth, titanium and zirconium to form by reaction with said alkaline filler substantially white substantially water insoluble compound of said selected metal and substantially water insoluble compound of alkaline earth metal radicle of said alkaline filler.

24. In a method of manufacturing substantially white paper filled with alkaline filler comprising substantially water insoluble alkaline earth metal compound, those steps comprising applying to a paper web containing such alkaline filler an alkaline reacting solution of a compound of a metal selected from the group consisting of barium, zinc, lead, tin, antimony, bismuth, titanium and zirconium, and an acid reacting precipitant for said solution, to form substantially white substantially water insoluble compound of said selected metal and compound of alkaline earth metal radicle of said alkaline filler.

25. In a method of manufacturing substantially white paper filled with alkaline filler comprising substantially water insoluble alkaline earth metal compound, that step which comprises effecting the precipitation in a paper web containing such alkaline filler of substantially white substantially water insoluble compound from a webapplied solution of a compoundof a metal selected from the group consisting of barium, zinc, lead, tin, antimony, bismuth, titanium and zirconium, said alkaline filler being concurrently reacted upon.

26. In a method of manufacturing substantially white paper wherein there is employed alkaline filler'comprising substantially water insoluble alkaline earth metal compound, that step which comprises effecting the precipitation in a paper web of substantially white substantially Water insoluble compound from a web-applied solution of a'compound of a metal selected from the group consisting of barium, zinc, lead, tin, antimony, bismuth, titanium and zirconium, there being formed in said web in association -with said precipitated compound by an action upon said alkaline filler a compound of alkaline earth metal radicle of said alkaline filler.

HAROLD ROBERT RAFION. 

